Many grenades require no aim. Every class has access to sticky nades. Lightning and arcbolt grenades require just as much aim as firebolt. Lightning grenades are more likely to net you kills as they last longer on the field and often surprise people making them a much stronger choice. The argument I made about Sunsinger nades being up there is because their super allows them to be spammed but you disregard that and interpret it as ease of use when it's just as easy an other grenades.